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Randalf · 10-18-2016, 03:44 PM

We have a 2016 Ram 2500 4X4 and I put Firestone air bags on the rear before starting to tow our 2015 Chapparal 336TSIK fifth wheel (12k total, 2k on the pin). When I inflate the bags I put them at 30 psi, but I often don't bother with them because they make less than 2" difference in ride height, and I haven't noticed a difference in ride quality.
The truck came equipped with Firestone tires that only have a so-so rating, and I never bothered to rotate them. My thought was the sooner I wore them out, the sooner I could justify buying newer, cooler tires like Goodrich KO2's or Michelin A/T's The tires now have 27,000 miles on them, with 4,000 of those miles towing our fifth wheel.
The front tires still look great, with no cupping or scalloping. The outer and center treads of the rear tires also look great, but the inside of both rears are worn down well into the wear bar, and need to be replaced ASAP.

So, what would cause the rear tires to wear out only on the inside of the tread? I showed them to my mechanic, and he had no explanation. He said there are no caster or camber adjustments to be made on a 2500 solid axle, and wondered whether the axle housing is bent. Whaddaya think?

IC2 · 10-18-2016, 04:21 PM

Quote:

Originally Posted by Randalf

We have a 2016 Ram 2500 4X4 and I put Firestone air bags on the rear before starting to tow our 2015 Chapparal 336TSIK fifth wheel (12k total, 2k on the pin). When I inflate the bags I put them at 30 psi, but I often don't bother with them because they make less than 2" difference in ride height, and I haven't noticed a difference in ride quality.
The truck came equipped with Firestone tires that only have a so-so rating, and I never bothered to rotate them. My thought was the sooner I wore them out, the sooner I could justify buying newer, cooler tires like Goodrich KO2's or Michelin A/T's The tires now have 27,000 miles on them, with 4,000 of those miles towing our fifth wheel.
The front tires still look great, with no cupping or scalloping. The outer and center treads of the rear tires also look great, but the inside of both rears are worn down well into the wear bar, and need to be replaced ASAP.

So, what would cause the rear tires to wear out only on the inside of the tread? I showed them to my mechanic, and he had no explanation. He said there are no caster or camber adjustments to be made on a 2500 solid axle, and wondered whether the axle housing is bent. Whaddaya think?

I sure would suspect a bent housing or maybe a couple bad bearings, but that is only an outside possibility. An alignment shop should be able to tell you if there is a problem if they have a 4 wheel alignment rack even though they can't make any adjustment. Nothing else you have described would cause that problem

Skip426 · 10-18-2016, 04:38 PM

]I sure would suspect a bent housing or maybe a couple bad bearings, but that is only an outside possibility. An alignment shop should be able to tell you if there is a problem if they have a 4 wheel alignment rack even though they can't make any adjustment. Nothing else you have described would cause that problem[/QUOTE]

A shop with 4 wheel alignment equipment can tell if the housing is bent.

You list 2k as the pin weight, + the weight of the hitch, did you check what payload was available on the rear axle of the truck , before you started towing the 5er.?

Fishalaska1 · 10-18-2016, 07:35 PM

Over inflation? What is PSI? Do you mean frame side or middle of the tire?

Randalf · 10-18-2016, 08:00 PM

Skip426, I haven't weighed my rig yet, but I was very careful to keep all the numbers within limits based solely upon the manufacturers stated limits and weights. I can't remember offhand what the axle rating is for my 2500, but it was the governing factor for me, the one I was most likely to exceed. In order to keep the GAWR down, I had a B&W rollover ball installed in the truck, and a gooseneck adapter put on the trailer. The truck weighs 7700 pounds when fully loaded with fuel, people and luggage. It has a lightweight cross-bed aluminum toolbox behind the cab with maybe two hundred pounds of stuff in it, otherwise the bed remains empty. According to the factory sticker, the empty trailer weight is 11,200, and the max allowed weight with cargo is 12,300, I think. The factory sticker also lists the pin weight at 1800 pounds, so I rounded up to 2k in my planning. We are nowhere close to carrying the max amount of distributed cargo, and haven't added any extra permanent weight (batteries, generator, etc) up in the nose of the trailer.

We've taken the trailer once from central Texas to Ruidoso, NM, and back over roads that have been brutalized by oilfield traffic. A couple months ago we traveled that same route up to Durango CO, then on out through UT, NV, CA, AZ, NM and home. We travel 55 to 65 mph, depending on conditions. Is it possible that pounding up and down over those rough roads could have induced a bend in the axle? If I take the truck back to the dealership for warranty work, are they going to say: 1) you voided your warranty by adding aftermarket Firestone airbags, and 2) you damaged the axle by point-loading it with a ton of weight and driving 4,000 miles over rough roads?

Randalf · 10-18-2016, 08:12 PM

Fishalaska1, I have the front tires at 65 psi and the rear tires at 75, which were the pressures the salesman at the dealership recommended. The fronts look great, and the rear tire treads look fine from the outside edge to about 2/3rds of the way in. It is only the inside 1/3 of the tread that is worn down into the wear bar. The truck is in the shop right now for hail damage repair, or I'd post a picture.

wingnut60 · 10-18-2016, 08:38 PM

Like others, can't figure out what would cause this on the REAR axle. I think you ought to have a really good axle shop that can align four wheels (road force? maybe) look at it.
If this were a trailer axle, I would say overloaded or lost camber...
Just for grins, check out the shocks to eliminate that possibility.
And, also, get the combo weighed.
Joe

Randalf · 10-18-2016, 08:53 PM

I just checked the Dodge Ram towing chart for a crew cab 4X4 with 6.4 Hemi, and came up with these numbers:

GVWR- 10,000
Payload- 3300
Base weight- 6702 total, 3865 front, 2838 rear
GAWR- 5500 front, 6,000 rear
GCWR 19,800
Max trailer- 12,600

These numbers are for 3.73 differentials, a switch to 4.11 would gain me 3,000 in GCWR & max towing capacity, but nothing changes GAWR rear.

As I said, I figure I'm really close to the max on GAWR rear, but still within specs. Wingnut 60, I do plan to take it to the Cat Scales as soon as I can to find out the real deal on weights.

cashmore · 10-18-2016, 08:59 PM

Have you checked the end play tolerance measurements on the rear bearings?

Rickeoni · 10-18-2016, 09:10 PM

Sounds like over inflation, what is the size of tire and max inflation on the sidewall?

wingnut60 · 10-18-2016, 09:32 PM

Randalf,
You have an odd problem, and many others probably tow close to or over more than you are, without the tire problem.
Hope you find an answer and let us know.
Joe

Randalf · 10-19-2016, 02:47 PM

Alrighty then, the official results are in!
I took the truck to the dealership, and they sent me to a private alignment shop to have it checked out. Turns out the right side of the axle is slightly bent, apparently at the weld point with the hub. The tech said the paint was cracked in that area. The bend is very slight, but no adjustments can be made, so the axle needs to be replaced or it will continue wearing out tires.
I have an appointment Friday morning at the dealership for them to assess the problem and see what they are willing to do about it. I don't know whether they'll fix it without a fight, or try to blame me for the damage. I'm afraid they'll say I voided the warranty when I installed air bags (the same Firestone bags they install as a factory option), or claim I towed too heavy a load over roads that were too rough. Stay tuned!

cashmore · 10-19-2016, 02:59 PM

Thanks for the update, sorry about all the trouble. At least you now know what the issue is and can begin to get the fix in. Please keep us updated.

wingnut60 · 10-19-2016, 03:06 PM

First time ever hearing of such--as to the air bags, no way, but they might claim that caused it. In that case, you need to talk to whoever installed them.
At least you know, and the fix is straightforward simple labor, altho I would think both axles shafts and the bearings need to be replaced, along with the axle housing. Would think the 3rd member would be ok.
Joe